Circuit for vapor generator



June 1954 R. A. KANE CIRCUIT FOR VAPOR GENERATOR Filed July 27, 1961 Fig. l.

3 Sheets-Sheet l u 1 a u INVENTOR Robert A. Kane ATTORNEY June 2, 1964 Filed July 27, 1961 3 Sheets-Sheet 2 J 40 48 INVENTOR Robert A. Kane ATTORNEY June 2, 1-964v R. A. KANE 3,135,251

CIRCUIT FOR VAPOR GENERATOR Filed July 27. 1961 s Sheets-Sheet a 0 INVENTOR 1, 11,, 48 0 Robert A. Kane 86 8 ATTORNEY United States Patent CIRCUIT FOR VAPOR GENERATOR Robert A. Kane, Hazardville, Conn, assignor to Combustion Engineering, Inc., Windsor, Conn., a corporation of Delaware Filed July 27, 1961, Ser. No. 127,331 11 Claims. (Cl. 122-406) This invention relates generally to the art of vapor generation and is particularly concerned with an improved vapor generator organization for operation at supercritical pressures.

The invention provides an improved supercritical vapor generator organization with tubular panel wall construction being employed in the furnace and in the gas pass leading from the furnace and with the arrangement having an economic piping layout so that the most advantageous routing or flow of the through-flow is had so as to provide a minimum of connecting piping from one heat exchange portion to another.

The characteristics of the Working medium at supercritical pressures and temperatures are such that natural circulation and separation of liquid and vapor as recognized in subcritical operation are either not possible or not satisfactory so that supercritical vapor generators are of the forced once-through flow type wherein the feed pump forces the working medium through a continuous circuit from the inlet of the vapor generator to its outlet with the feed being regulated in accordance with the output of the unit and with the working medium being heated to its desired temperature during passage through the unit, this medium being delivered at this desired temperature and the desired pressure to the point of use, as for example a turbine.

Since there is no heat of vaporization at and above supercritical pressure the temperature of the working medium progressively increases as it traverses through the once-through flow system with each increment of heat imparted to the working medium resulting in a rise in temperature of the medium. This effect necessarily poses a problem in connection with welded panel walls in such a unit. This is so because the tubes which make up such a wall will increase in temperature throughout their length and if the tubes are in parallel flow relation adjacent tubes may vary significantly in temperature particularly toward the tube outlet as a result of variation in flow or variation in heat input.

Notwithstanding the problems connected with welded panel wall type of construction, for economy, ease of fabrication and erection, as well as other various significant purposes, it is extremely desirable to be able to employ this type of wall construction in these generators. This is particularly true in the furnace and the gas pass communicating with or leading from the furnace outlet, with it being desired to have these panels provide generally pressure-tight walls thereby simplifying fabrication, erection, and support and yielding a construction which may be readily hung from its upper end and eX- pand downwardly.

In the forced once-through flow type of system since the amount of working medium which flows through the system is dependent upon the actual load upon the vapor generator, this amount will vary as the load changes. Accordingly, there is a minimum load at which the flow through the tubes is adequate to insure proper cooling thereof. This load is generally about 30 percent with this being considered a good working compromise in that the design can be reasonable and with adequate flow at the 30 percent load the pressure drop at maximum load is still not intolerable.

In order to obtain sufficient velocity through the tubes that line the walls of the vapor generator several tube ar- 31,135,251 Patented June 2, 1964 rangements have been employed. For example, a number of parallel flow tubes have been extended up and down the walls in ribbon fashion to form a tubular lining for the Walls with Patent No. 3,030,937 issued April 24, 1962, to E. C. Witzke, disclosing this arrangement. Groups of riser panels have been positioned in side-byside relation about the circumference of the furnace with each of the groups being connected at their lower ends with inlet headers and at their upper ends with outlet headers and with adjacent groups being connected in series flow relation, with this being known as the Benson" construction. In these arrangements the temperature variation between certain adjacent tubes on the wall is extremely high so as to make it extremely hazardous if not totally impracticable to provide a completely welded panel construction throughout the width of the wall.

If, in lieu of the aforementioned types of wall construction the walls of the forced once-through flow supercritical vapor generator are lined with side-by-side tubes, each adjacent one of which is in parallel flow relation and with the tubes along each wall being welded throughout the length of the wall into a panel, such an arrangement is subject to serious objections. Since the relationship between output of the unit and the circumference of the furnace that is required is fixed within definite limits a large number of parallel flow tubes are required to line the furnace so that even at a minimum 30 percent flow as previously mentioned, these tubes must have an unusually small diameter of about 1" or smaller in order that the necessary average fluid velocity will be provided through the tubes to insure adequate cooling of them. The restrictive eifect that deposits and tolerances in the tubes have upon tube temperature is substantially greater for these small diameter tubes than for tubes of larger diameter. Furthermore, if fins are employed on these relatively small diameter tubes there is presented an unfavorable area relationship of steel to fluid for heat transfer purposes. In addition these panels have a rather low flexibility to accommodate thermal displacements. Beyond these objections there is the very serious problem of non-uniform temperature distribution throughout such panels that line each of the walls. Tubes in different 10- cations of the furnace will be subjected to very different heat inputs or heat absorption so that across the walls of the furnace the tubes that make up the panels will receive varying amounts of heat. This is especially true as concerns furnace wall tubes for low loads and in particu lar under start-up conditions since at this time the ratio of furnace heat absorption to over-all absorption is at its peak and the entering or feed water temperature is less. This requires, on the one hand, that measures be taken to increase stability within the tubes, such as orifices to control the pressure drop through the tube, and, on the other hand, leads to considerable thermal stresses across the panel Width. As a result of starting the unit and changing load on the unit these stresses vary so that a cyclic stress condition is set up which is susceptible of causing fatigue failure over a period of time.

The variation of these stresses with changing load is caused among other things by variation of the temperature difference between the inlet and the outlet of the tubes of the panels with varying load and variation of the heat absorption transversely of the furnace wall with varying load. The higher the temperature difference between inlet and outlet the greater the danger of there being a considerable outlet temperature unbalance across the panels and around the furnace circumference, with this being more fully explained in the application entitled Furnace Wall Arrangement for Vapor Generator, application Serial Number 127,396, filed in the name of Willburt W. Schroedter on July 27, 1961, now Patent No. 3,135,243 of June 2, 1964, and having a common assignee.

In accordance with the present invention there is pro vided a once-through flow supercritical vapor generator wherein the walls of the furnace are lined with tubular panels and wherein the walls of the gas pass or at least some of the walls of the gas pass are also lined with tubular panels with the circuit being such as to require a minimum of piping which merely serves the purpose of carrying the working medium from one heat exchange portion of the through-flow system to another. As embodied, the tubular panels which line furnace walls are comprised of side-by-side tubes extending longitudinally of the furnace with each adjacent tube being in parallel flow relation with regard to the working medium and with the tubes that line each wall of the furnace being welded throughout the length of the furnace so as to provide an imperforate structure. The panels lining the gas pass walls may be similarly constructed, although if desired, the adjacent tubes in these panels lining the gas pass may be free of each other rather than being welded together since such a structure, for economic reasons, may be preferable in certain instances in this region of the vapor generator wherein the operating conditions are not as severe as they are in the furnace. In a preferred embodiment of the invention, the furnace is provided with a vertically extending partition wall which is also constructed of a welded tubular panel and which is connected into the through-flow system in an advantageous manner to both simplify piping requirements and to take greatest advantage of existing operating characteristics. In accordance with the invention the design of the tubular panels that line the furnace and the gas pass walls and that make up the partition wall is not limited by requirements of the through-flow system of the supercritical vapor generator and the tube temperatures that prevail in each of the panels is more uniform than would otherwise be had, with stresses, particularly in the welded panel walls resulting from differential temperatures, being maintained relatively low. These advantageous results are achieved by superimposing a circulating system on the once-through flow system with this circulating system being in parallel or connected across the panel walls and being effective to supplement the through-flow through the tubes that make up these walls. By supplementing the through-flow in the tubes that make up the panel walls, the temperature rise between the inlet and the outlet of the tubes particularly during start-up and at low loads is greatly reduced being only a fraction of the value that it would be without the supplemental flow. This supplemental flow also reduces the possibility of unbalance of fluid temperature in the tubes across the panel and accordingly unbalance of the tube metal temperatures. This is so whether this unbalance in fluid temperature is caused by flow variation due to tube geometry or by uneven heat absorption.

The reduction of temperature rise between inlet and outlet further improves the stability of flow between the heated parallel tubes, which is principally a function of the properties of the fluid along the heated path. This increase in stability in turn reduces the possibility of tem perature unbalances.

In addition to providing a more uniform temperature distribution this superimposed circulating system on the once-through flow system enables the designer to design the tubular panel walls in accordance with considerations other than those dictated by the once-through flow system. The tube size may be selected for the one best suited for the requirements of the service. It will be sufficiently large to avoid any substantial effect or influence by mill tolerance and deposits on pressure flow and temperature. The tube wall thickness can be selected on the basis of pressure and temperature considerations only, which is not the case in a panel wall construction in a supercritical through-flow generator without the circulating system of the invention, since in such case the wall thickness of uniform outside diameter tubes may have to be increased beyond that necessary for the temperature and pressure considerations in order to reduce the inside diameter and provide an area which will give the necessary flow velocity through a critical portion of the tube. The circulating system of the invention permits the panel geometry, i.e., the relationship of outside diameter, wall thickness, spacing, fin placement and size, to be selected so as to provide improved panel flexibility as well as a surface pattern best suited to the operation of the unit.

It is an object of the present invention to provide an improved once-through flow supercritical vapor generator.

A further object of the invention is to provide a supercritical once-through flow vapor generator of an improved design having an elongated furnace and a gas passageway extending therefrom with the furnace and the gas passageway having walls lined with parallel flow side-by-side tubes that make up a panel and with the arrangement being such that wide variation in tube temperature in each panel is inhibited and a simplified and economic piping arrangement is provided.

A still further object of the invention is to provide such a supercritical once-through flow vapor generator with a panel type furnace partition wall connected into the through-flow circuit in a most efiicient and expeditious manner, insuring adequate cooling of the tubes thereof and providing a simple piping layout.

Other features and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate a preferred embodiment of the invention and in which:

FIGURE 1 is a vertical sectional view of a oncethrough flow supercritical vapor generator embodying the present invention with this view being somewhat diagrammatic in nature;

FIGURE 2 is also a vertical sectional view somewhat diagrammatic in nature with this view being taken generally along line 2-2 of FIG. 1;

FIGURE 3 is a transverse section taken generally along line 33 of FIG. 1;

FIGURE 4 is a skeletonized perspective view of the vapor generator of FIG. 1 showing how the various walls of the furnace are interconnected with the through-flow system and with the superimposed circulating system; and

FIGURE 5 is a fragmentary sectional view through one of the side Walls of the vapor generator.

Considering now in detail the illustrative organization depicted in the drawing, the once-through flow supercritical unit shown therein includes furnace 10 which is vertically disposed and has an outlet for combustion gases at its upper end and provided in its rear wall. Extending from this outlet is the lateral gas pass 12 which connects with the upper end of the vertically extending gas pass 14 that extends downwardly in parallel relation with the furnace. Combustion gases pass up through furnace 10 through the outlet and then through gas passes 12 and 14 with the gases being conveyed from this latter gas pass to a stack and traversing, as is conventional, a suitable air heater or other heat exchange equipment.

As illustratively disclosed furnace 10 is fired by means of tangentially arranged burners 16 which are disposed to provide a whirling gas mass in the two furnace compartments 18 and 20, FIG. 3. While tangential type of firing has been illustratively disclosed in the drawings other well-known types of firing may be employed with the inventive organization, as for example either the horizontal or vertical cyclone type firing may be used where crushed coal is burned in cyclone chambers or front-wall or opposed-wall firing may be employed. The so-called turbo firing may also be utilized wherein burners, horizontally arranged on opposite walls, are directed downwardly to- Ward the furnace bottom. Regardless of the type of firing employed hot combustion gases are generated in the lower region of the furnace 10 and pass upwardly therethrough and out the outlet at the upper portion of the furnace.

The furnace is made up of front wall 22, rear wall 24,

and side walls 26. Centrally disposed between side walls 26 is partition wall 28 which extends between but terminates, at least throughout a major portion of its length, in spaced relation with front and rear walls 22 and 24 with the partition wall 28 dividing the furnace into the aforementioned compartments 18 and which extend vertically throughout the height of the furnace.

The once-through flow system of the vapor generator is comprised of a number of heat exchange portions or sections which are connected in series flow relation and through which the through-flow is forced by means of the feed pump. For convenience of identification these heat exchange sections may be identified as the economizer, the wall tube heating sections and the heating sections comprising tubular members extending down into the gas passageways and the furnace.

Feed pump 39 forces the working medium through the economizer 32 which is comprised of numerous tubular elements in parallel flow relation and positioned generally at the lower end of gas pass 14. From economizer 32 the through-flow is conveyed to header 33 and then through conduit 34 to mixing vessel 36 and from this mixing vessel the fluid flows down through conduit 38 to the inlet header 40 positioned at the bottom of center wall or partition wall 28. t

This partition wall 28 is comprised of vertically extending side-by-side tubular members 29 which are connected at their lower end with the header 4t) and at their upper end with header 42. Alternate tubes of the center wall are bent at the lower end of the wall (FIG. 2) in order to form one side of the hopper bottom for each of the furnace compartments, Each adjacent tube in the center wall is in effect a separate tube that extends only once throughout the length of the center wall being connected at its upper and lower ends to the outlet and inlet headers of the wall respectively. The working medium flows up simultaneously through all of the tubes of the center wall from header 4% to header 42 in parallel flow relationship through the various tubes. From outlet header 42 the working medium is conveyed through conduit 43, which in FIG. 3 forms an extension of header 42, to the distribution header 45.

As illustratively disclosed, the inner walls of gas pass 14 are lined with vertically extending side-by-side tubes downwardly through which the working medium flows. These tubes which are identified in FIGS. 1 and 3 as 47 and which line the front wall 49 and rear wall 51 of gas pass 14 extend laterally from header 45 in opposite directions as shown and then extend downwardly and along the inner surface of the respective wall. The tubes 47 which line the side walls of the gas pass extend downwardfrom side headers 53 which are connected with the ends of distribution header 45. The tubes 47 that line each of the walls of the gas pass are disposed in side-byside relation in the same manner as the tubes that make up the center partition wall and the tubes that line the furnace wall. Adjacent tubes 47 may be welded together throughout the extent of the walls they overlie, although there may be instances where it is desired not to have these tubes welded to form an imperforate structure. The lower ends of the tubes 47 are connected with ring header 5'7 and from this header the working medium is conveyed downwardly through the rest of the height of the vapor generator by means of downcomer 44 and to the inlet header means designated generally 46 which serves the tubes that line the furnace walls.

This header means includes the headers 48 to which are connected the lower ends of tubes 59 that are disposed in side-by-side relation and extend vertically up along the furnace side walls 26 connecting at their upper end with outlet headers 52. The header arrangement 46 also includes header 54 to which the lower end of tubes 56 are connected with these tubes being in side-by-side relation and extending vertically up along front wall 22 being bent at their upper region to extend along the roof of the furnace and then connect with outlet header 58. Also forming part of the header arrangement 46 is header 60 to which the lower ends of tubes 62 are connected with these tubes being disposed in side-by-side relation and extending up along the rear wall 24 of the furnace with some of these tubes 62 being bent to extend along and conform with nose baffle 64 While others continue their vertical extension across the back of the nose bafile with the tubes 62 extending across gas pass 12 and connecting at their upper end with outlet header 58.

The headers52 are interconnected with header 5% and from header 58 the working medium may be conveyed to mixing vessel 36 through conduit 88 or to a heat exchange bundle in the upper end of gas pass 14 via conduit 69. This heat exchange bundle is comprised of a group of sinuously bent tubes through which the working medium is conveyed with the outlets of these tubes being connected to header 74. From header 74 the working medium is conveyed through conduit 53 to header 7 8. Connected with the latter header is the inlet of the tubes which make up the panel type heat exchange portion that extends down into the upper end of the furnace and is comprised of a plurality of panels disposed in side-by-side relation across the furnace. In traversing the panel heat exchange portion $9 the fluid is heated to its desired temperature and is at its desired supercritical pressure and accordingly is delivered to the high pressure portion turbine 82.

As disclosed the unit is provided with a reheater 84 disposed in gas pass 12 and which is connected with the turbine 82 in the usual manner to reheat the vapor after it has given up a portion of its energy, supplying reheated vapor to the low pressure portion of the turbine.

The exhaust from the turbine 82 is received in condenser 83 where the vapor is condensed and this condensate is pumped by a pump 85 through feedwater heaters 87 and deaerator 89 to the inlet of feed pump 30.

Each of the side-by-side tubes that line the inner surface of the furnace walls 22, 24 and 26 are in effect separate tubes which extend between the inlet and outlet headers of the respective walls with each adjacent tube being in parallel flow relation so that all of the tubes lining the furnace walls are in parallel flow relation with the through-flow passing upwardly through these parallel flow paths. Adjacent tubes on each wall are welded together throughout the length of the wall with the juncture of the tubes being shown in FIG. 5. As illustratively disclosed, in FIG. 5, tubes 50 are joined together throughout the length of the wall by providing spacer 86 between each adjacent pair of tubes and welding this spacer to the tubes throughout the wall length.

By welding adjacent tubes along each of the furnace walls throughout the length of the furnace wall a generally imperforate gas tight tubular inner casing or lining is formed which simplifies wall construction and goes a long way towards providing a pressure resistant gas-tight furnace. panels together at the corners of the furnace and throughout the panel height so that longitudinally extending seals may be omitted for the furnace and so the inner tubular wall construction provides a complete, gas tight encasement. The center wall is also preferably of welded construction in order to provide greater strength and in order to provide a surface to which slag is much less likely to adhere. As previously mentioned, the center wall throughout a major portion of its length terminates in spaced relation with the front and rear walls of the furnace in order to provide a suitable opening or passage between the compartments l8 and 2% for pressure equalization and other purposes.

The tubes 4'7 that line the walls of gas pass 14 are arranged similarly to those that line the furnace walls and that make up the center partition wall. Each of the tubes 47 is in effect a separate tube which extends downward from the inlet header to the outlet header of the respective Furthermore it is preferred to weld adjoining wall of the gas pass with each tube being in parallel flow relation so that there is only downflow of the working medium from the inlet header to the outlet header through the tubes 47. It is preferred that the tubes 47 where they overlie the walls of gas pass 14 be welded together in the same manner as the furnace wall and the partition wall tubes so as to provide an imperforate or generally imperforate surface or layer thereby simplifying the construction of the gas pass in connection with providing a gas tight wall. As previously mentioned there may be instances, however, where for economy or other purposes adjacent tubes 47 may be free of each other and not welded together throughout the overlying extent of the gas pass wall.

By connecting the partition wall in series flow relation with the furnace wall tubes the effective total flow area is substantially less than if a parallel flow arrangement were adopted so that the flow velocity through the center wall and furnace wall tubes for a given through-flow is substantially greater.

It is noted thatthe flow area provided by the center Wall tubes is substantially less than the flow area provided by either the tubes 47 lining the gas pass wall or the tubes lining the furnace wall as for example being onequarter the area of the furnace wall tubes. It is further noted that the center wall is upstream relative to flow of the working medium with respect to both the gas pass wall tubes and the furnace wall tubes. This is a very advantageous arrangement in that the combination of having the center wall of a smaller flow area and upstream of the gas pass and the furnace walls provided the furnace center wall with a greater flow velocity of the working medium with the Working medium passing up through the center partition wall being both cooler and having a lower specific volume than that passing through the gas pass wall tubes and the furnace wall tubes. Since the center partition wall is subjected to very severe operating conditions receiving intense heat on both sides from both furnace compartments this higher flow velocity, lower temperature and lower specific volume, all tend to insure adequate cooling of the partition wall tubes.

In order that the through-flow through both the center partition wall and the furnace walls may be supplemented in order to overcome the very serious objections which otherwise prevail with the wall arrangement of parallel flow tubes and particularly with the welded wall construction in a once-through supercritical unit there is provided a circulating system superimposed on the throughflow system for recirculating a portion of the working fluid through the tubes that make up these wall portions. This circulating system includes conduit 88 which as previously mentioned is connected with header 58 that receives the working medium egressing from the tubes extending up along the furnace walls. This conduit 88 is connected with pump 90 which has its outlet connected with mixing vessel 36. Accordingly, through this circulating system which is effectively connected in bypass rela= tion or across the combined center wall, gas pass wall and furnace wall heat exchange portions a portion of the working medium may be reintroduced into and be circulated through these heat exchange portions. Therefore the fluid flow through the tubes which make up the center partition wall, gas pass wall and the furnace walls may be supplemented with respect to the through-flow and accordingly is not restricted to the through-flow.

The unit may be designed so that in its upper load range no recirculation is necessary since in this range the through-flow is sufliciently great to provide ample velocity through the center wall and furnace wall tubes without encountering the objections hereinbefore mentioned. However, as the load is decreased on the unit and the throughflow accordingly decreased it is necessary to supplement the through-flow through the center partition wall and the furnace wall tubes and accordingly as the load decreases the circulating system is effective to circulate the working medium or a portion of the working medium through these portions of the through-flow system.

As an illustrative example the circulating pump may be a constant speed pump and may be so designated that at 70 percent load it becomes effective to initiate circulation through the center partition wall and the furnace wall tubes. As the load on the unit decreases this constant speed pump will be effective to maintain the velocity through the center partition wall, the gas pass wall and the furnace wall tubes adequate to insure against tube failure and of course as the load decreases the pump will be effective to circulate a greater proportion of the total flow through the center partition and furnace wall tubes.

In the connection between the pump 90 and the mixing Vessel 36 there is preferably provided a check valve 92 to prevent reverse flow through the pump and conduit 88.

Center partition wall 28 and the furnace Walls are connected in series flow relation in order to decrease the differential temperature between the inlet and the outlet of the tubes making up these wall portions. Whether these wall portions are connected in parallel or in series flow relation the amount of heat that must be absorbed by the fluid flowing through them would have to be the same, since this would be a requirement in order to meet the load imposed upon the vapor generator. It is, accordingly, apparent that the difference in temperature in the working medium entering and leaving these wall portions will be substantially less if they are connected in series than if they are connected in parallel. This hecomes obvious when it is considered that when connected in series the heating of the working fluid from its initial temperature upon entering the center wall to its final temperature upon leaving the furnace walls is accomplished in two stages while with a parallel flow arrangement this temperature increase would be effected in a single stage.

The circuit arrangement of the invention is particularly advantageous in that it provides upflow through the parallel circuits that make up the center wall and also the parallel circuits that make up the furnace wall lining with upflow being extremely desirable in these furnace portions or heat exchange portions because of the very high rate of heat exchange and with there being downflow provided in the tubular wall lining for the gas pass 14 and where the heat transfer is considerably less than in the furnace so that the downflow is not objectionable. For stability reasons it is extremely desirable to have upflow in the parallel flow circuits where high heat absorption is encountered. If this requirement is not observed serious stability problems may be encountered where the tubes that make up the parallel flow circuits will have different amounts of fluid flowing through them.

With the arrangement of the invention a very economic piping layout is achieved with the downflow tubes 47 conveying the fluid is a substantial portion of the distance from the upper end of the vapor generator down toward the bottom thereof for introduction into the furnace walls at the lower end of these walls and for upflow through the walls. By having the circuitry laid out so that the fluid flows up through the center wall then down'through the walls lining the gas pass 14 and then up through the furnace wall tubes the amount of piping required merely to convey the fluid from one of the heat exchange portions to the other is greatly reduced. In this respect it is noted that the downcomer or downcomers 44 need only be approximately half the height of the unit. When it is considered that these supercritical units are operating at pressures above 3,200 lbs. per square inch and when it is considered that the temperature of the fluid which these conveying conduits or downcomers handle is relatively high as Well as the quantity of the fluid being very large, it is appreciated that these conduits are costly so that it is extremely desirable that the extent of such conduits be maintained at a minimum.

It is the superimposing of the circulating system on the once-through flow system of the supercritical vapor generator that permits the parallel tube lining of the furnace and gas pass walls in the manner described with suitably large tubes to obtain optimum operating results including greater stability because of decreased fluid temperature differences longitudinally of the tube and less stress because of more uniform tube temperatures tranversely of the panels.

Since all of the tubes that make up the panels on the furnace walls are in parallel flow relation they will all generally be at the same temperature so that the furnace may be hung from above and will expand vertically downward. For this purpose hanger rods 93 may be provided which extend down from structural steel members, as shown (FIG. 1), and are connected with some of the tubes on each wall. The welded tubular panel Wall type of construction greatly simplifies support of the unit and construction of the furnace walls permitting a known and proven wall design, including buck stays and their supports to be employed. It will be appreciated that the entire wall structure may be supported from the inner tubular panels. With regard to the gas pass 14 the tubular panel arrangement whereby parallel flow tubes line the walls of the gas pass is of substantial advantage in the arrangement of the invention wherein these tubular walls form part of the circulating system through which the working fluid, in supplement to the through-flow, is conveyed in that, as a result of the circulation of the working medium, the parallel flow tubes are maintained at a more nearly uniform temperature. This is desirable even if the adjacent tubes that line the walls of the gas pass are not welded together, which in some instances may be a desirable form of construction for these gas pass walls. The desirability of having more uniform tube temperatures is evident when it is considered that the tubes form the support for the entire wall, i.e., the outer wall portions are supported from the tubes. Therefore by having the tubes at a more nearly uniform temperature differential expansion problems are considerably lessened.

While in the illustrative arrangement the entire wall surface, i.e., all four walls of the gas pass 14 have been disclosed as lined with parallel flow tubes 47, the advantages of the invention may be obtained by lining less than all of the walls of the gas pass with these tubes 47. For instance, only two of the walls, as for example the front and rear wall, or the side walls may be lined with the parallel flow tubes 47 while the other walls may have tubes from other heat exchange portions disposed on the surface thereof. These tubes 47 would be connected into the circuit in the same way as previously described and accordingly achieve the desired results as mentioned hereinbefore.

Accordingly it will be seen that by means of the present invention there is provided a once-through fiow vapor generator designed to operate at supercritical pressures and which is provided with a novel organization which enables the tubular panel wall type construction to be employed while providing for freedom of design with regard to the tubular panels and maintaining the stresses developed within the panels during operation at a minimum, and further which provides an economic piping arrangement.

While I have illustrated and described a preferred embodiment of my invention it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall within the purview of my invention.

What is claimed is:

l. A supercritical vapor generator including a tubular through-flow circuit through which the working medium is forced at supercritical pressure, an elongated furnace having firing means near one end and a combustion gas outlet remote therefrom, passageway means extending from the outlet and alongside the furnace, a furnace partition wall comprised of longitudinally extending tubular members and forming part of said circuit, tubular members lining at least a portion of the walls of the passageway and forming part of said circuit downstream with relation to flow through the through-flow circuit of said partition wall, and additional tubular members lining walls of the furnace and also forming part of the circuit but downstream with relation to flow through the through-flow circuit of the passageway wall tubes, a circulating system superimposed on the through-flow system and connected to provide a supplemental flow through said furnace wall tubular members over and above the through-flow.

2. A once-through flow supercritical vapor generator comprising an upright furnace fired at a region remote from one end to thereby create a gas stream, and having an outlet for combustion gases at said one end, a gas pass extending from said outlet and in adjacent relation to the furnace and through which the gas stream passes; a tubular through-flow circuit through which the working medium is forced, said circuit including an economizer in the gas pass, a partition wall in the furnace comprised of separate side-by-side parallel vertically extending tubes, means supplying the working fluid after it has passed through the economizer to the lower ends of the tubes for passage upwardly therethrough, wall means in said gas pass provided with vertically extending tubes, means supplying the working fluid after it has passed through the tubes of the furnace partition wall to these tubes of the gas pass wall, tubular members disposed on and lining walls of the furnace and in series flow with but downstream of the gas pass wall tubes relative to the flow through said circuit and additional tubular heat exchange surface disposed within said gas stream and receiving the working medium after its traversal of said tubular members disposed on walls of the furnace.

3. A once-through flow supercritical vapor generator including a vertically disposed furnace defined by wall members, fired at its lower region and having an outlet for combustion gases at its upper region, a gas pass extending from said outlet downwardly in parallel relation with the furnace, tubes lining the several walls of the furnace, a generally centrally disposed partition wall in the furnace comprised of tubes, and tubes lining the gas pass wall, said partition wall tubes, said gas pass wall tubes and said furnace wall tubes being respectively in series flow relation and with the tubes at each location being separate parallel and vertically disposed in side-byside relation with adjacent tubes being bonded together, these tubular Wall portions forming part of the throughflow system of the vapor generator, means conveying the through-flow from the upper end of the partition wall tubes to the upper end of the gas pass wall tubes and from the lower end of the gas pass wall tubes to the lower end of the furnace wall tubes, a circulating system effectively connected between the outlet of the furnace wall tubes and the inlet of the partition wall tubes to provide a circulation of the working medium in supplement to the through-flow through the partition wall, the gas pass wall and the furnace wall.

4. A supercritical vapor generator provided with a through-flow circuit and including an upright furnace and a vertically extending gas pass leading therefrom and wherein the through-flow circuit includes first, second and third heat exchange portions connected in successive relation, said first portion comprising separate vertically extending tubes in side-by-side, parallel flow relation forming a furnace partition wall and connected into the through-flow system so the flow is upwardly therethrough, said second portion comprising similarly arranged tubes lining the gas pass and connected for downflow receiving the working medium egressing from the upper end of the tubes of said first portion, and said third portion comprising similarly arranged tubes lining the furnace and connected for upflow receiving the working medium egressing from the lower end of the tubes of said second portion,

1 1 r additional heat exchange surface in the through-flow circuit connected to receive the through-flow from the upper end of the tubes of said third portion, a circulation system superimposed on the through-flow system being effective to receive a portion of the working medium egressing from said third portion and reintroduce it into the throughflow system upstream of said first portion for passage through the three portions in supplement to the throughflow.

5. In a supercritical vapor generator the combination of an upright furnace having fuel firing means in a region near one end and a combustion gas outlet remote therefrom and having its Walls lined with longitudinally extending tubular members welded together to form a generally imperforate structure, an upright furnace partition wall comprised of longitudinally extending tubular members, separate inlet header means at the lower region of the furnace and separate outlet header means at the upper region for the first-mentioned and second-mentioned tubular members, respectively, a vertically extending passageway communicating with said outlet and extending therefrom parallel with said furnace toward said one end and having at least a portion of its walls lined with longitudinally extending tubular members, inlet header means with which the upper ends of the last-mentioned tubular members are connected and outlet header means with which the lower ends are connected, said generator having a through-flow circuit, through which the supercritical pressure fluid is forced, with the tubular members of said furnace walls, said partition wall and said passageway wall forming part thereof, means interconnecting the outlet header means of the partition wall tubular members and the inlet header means of passageway walls tubular members and means interconnecting the outlet header means of these latter tubular members and the inlet header means of the furnace wall tubular members, and a circulating system superimposed on the through-flow system and operative to provide a flow through the tubular members of the furnace walls, the partition walls and the passageway wall in supplement to the through-flow.

6. A once-through flow supercritical vapor generator comprising an upright furnace having means for firing the same near one of its ends and a combustion gas outlet near the other end, a gas passageway extending from said outlet alongside said furnace in parallel relation therewith, a tubular through-flow circuit through which the working medium is forced under supercritical pressure, this circuit including several heat exchange portions connected in series flow relation and among which are a tubular furnace partition wall, a tubular furnace wall lining and a tubular gas pass wall lining, each of these tubular walls including numerous tubes which are in parallel flow relation with the tubes of the furnace wall lining being welded together so as to form a generally imperforate panel, means conveying the through-flow first through the partition wall tubes, thereafter through said tubes lining the gas pass, and then through the furnace wall lining tubes, and a circulating system superimposed upon the through-flow system and connected to receive a portion of the effluent from the furnace wall tubular members and effective to recirculate working medium through the tubular members lining the furnace wall in supplement to the through-flow.

7. A once-through flow supercritical vapor generator comprising an upright furnace and having firing means associated with a region of the furnace near one of its ends and having an outlet for combustion gases near its other end, a gas passageway extending from said outlet alongside said furnace in parallel relation therewith, a tubular through-flow circuit through which the working medium is forced at supercritical pressure, said circuit including an economizer tube bundle in said gas passageway, a tubular partition wall in said furnace and comprised of tubular members in side-by side relation, said partition wall being connected to receiving the throughflow after its traversal of the economizer, a tubular wall lining for the gas pass and comprised of tubular members in side-by-side relation welded together to form a generally imperforate structure and providing a lining for the inner surface of at least a portion of the gas passageway, said tubular lining being connected to receive the through-flow after its traversal of said partition wall, a tubular lining for the furnace and comprised of tubular members in adjacent relation and welded together to form a generally imperforate structure, said furnace wall tubular lining being connected to receive the through-flow after its traversal of the gas passageway tubular lining, additional heat exchange surface receiving the throughfiow effiuent from said furnace wall tubular lining and disposed to receive heat produced by the burning of fuel in said furnace, a circulating system superimposed upon said through-flow circuit and operative to provide a recirculation through a portion of the through-flow circuit comprised of the partition wall, the tubular gas pass lining and the tubular furnace lining, said circulating system being effective to provide a recirculation of working medium through this portion of the through-flow system and in supplement to the through-flow.

8. A once-through flow supercritical vapor generator comprising an upright furnace having firing means at its lower region and an outlet for combustion gases at its upper region, a gas passageway extending from said outlet and downwardly in adjacent relation to the furnace, a tubular through-flow circuit through which the working medium is forced at supercritical pressure, said circuit including in series flow relation an economizer in the lower region of the gas pass, a tubular vertically extending furnace partition wall, a tubular lining for the walls of the gas passageway, a tubular lining for the walls of the furnace and heat exchange surface extending into the gas stream that passes through the furnace and the gas passageway, the total flow area provided by the tubular partition wall being substantially less than that provided by the tubular lining for either the gas passageway or the furnace, these tubular linings being comprised of vertically extending tubes in side-by-side relation and in parallel flow with the adjacent tubes being bonded together throughout the length of the wall portion which they overlie so as to provide a generally imperforate inner metallic surface for the furnace and the gas pass, means including a mixing vessel for conveying fluid from the economizer to the lower end of the tubular partition wall, means conveying fluid from the upper end of the partition wall to the upper end of the tubular lining for the gas pass, and means conveying fluid from the lower end of this gas pass tubular lining to the lower end of the tubular lining for the furnace, a recirculating system superimposed on the through-flow system operative to establish a recirculation of working medium through a partition wall, the tubular lining for the gas pass and the tubular lining for the furnace, in supplement to the through-flow, said circulating system including means for conveying effluent from the tubular lining of the furnace walls to the mixing vessel.

9. A once-through flow supercritical vapor generator comprising an upright furnace and having firing means associated with a region of the furnace near one of its ends and having an outlet for combustion gases near its other end, a gas passageway extending from said outlet alongside said furnace in parallel relation therewith, a tubular through-flow circuit through which the working medium is forced at supercritical pressure, said circuit including an economizer tube bundle in said gas passageway, a tubular partition wall in said furnace and comprised of tubular members in side-by-side relation, said partition wall being connected to receive the through-flow after its traversal of the economizer, a tubular wall lining for the gas pass and comprised of tubular members providing a lining for the inner surface of at least a portion of the gas passageway, said tubular lining being connected to receive the through-flow after its traversal of said partition Wall, a tubular lining for the furnace and comprised of tubular members in adjacent relation and welded together to form a generally imperforate structure, said furnace Wall tubular lining being connected to receive the through-flow after its traversal of the gas passageway tubular lining, additional heat exchange surface receiving the through-flow effluent from said furnace wall tubular lining and disposed to receive heat produced by the burning of fuel in said furnace, a circulating system superimposed upon said through-fiow circuit and operative to provide a recirculation through a portion of the throughflow circuit comprised of the partition wall, the tubular gas pass lining and the tubular furnace lining, said circulating system being effective to provide a recirculation of working medium through this portion of the throughflow system and in supplement to the through-flow.

10. A supercritical vapor generator provided with a through-flow circuit and including an elongated furnace having a gas pass leading therefrom in parallel relation therewith, the through-flow circuit comprising a plurality of heat exchange portions connected in series flow relation including a tubular partition wall extending longitudinally of the furnace, a tubular wall lining for at least a portion of the gas pass, and a tubular wall lining for the furnace, the total flow area provided by the partition wall being substantially less than that provided by the tubular wall lining for the furnace and the partition wall being upstream with relation to flow through the throughflow circuit of the tubular wall lining for the gas pass which is in turn upstream with relation to flow through the through-flow circuit of the tubular wall lining for the furnace in said circuit.

11. The supercritical vapor generator of claim 10 wherein the tubular wall lining for the furnace is composed of side-by-side, parallel flow tubes welded together throughout the extent of the wall, and a circulation system is superimposed on the through-flow circuit in a manner to increase the flow through said partition wall, said tubular lining of the gas pass and said tubular lining for the furnace wall over and above that of the through-flow.

References Cited in the file of this patent UNITED STATES PATENTS 2,552,830 Witzhe May 15, 1951 2,962,005 Koch Nov. 29, 1960 FOREIGN PATENTS 831,175 Great Britain Mar. 23, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,135 ,251 June 2 1964 Robert A. Kane It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, linelO, before "furnace" insert the column 7, line 30, after "wall" insert be line 31,

column 8, line 54, strike read provides out "is"; column 11, line 28, strike out the comma; line 29, strike out the comma; same column 11, line 57, before "then" insert after these latter tubes for "provided Signed and sealed this 13th day of October 1964.

(SEAL) Attest:

EDWARD J. BRENNER ERNEST W. SWIDER Attesting Officer Commissioner of Patents 

1. A SUPERCRITICAL VAPOR GENERATOR INCLUDING A TUBULAR THROUGH-FLOW CIRCUIT THROUGH WHICH THE WORKING MEDIUM IS FORCED AT SUPERCRITICAL PRESSURE, AN ELONGATED FURNACE HAVING FIRING MEANS NEAR ONE END AND A COMBUSTION GAS OUTLET REMOTE THEREFROM, PASSAGEWAY MEANS EXTENDING FROM THE OUTLET AND ALONGSIDE THE FURNACE, A FURNACE PARTITION WALL COMPRISED OF LONGITUDINALLY EXTENDING TUBULAR MEMBERS AND FORMING PART OF SAID CIRCUIT, TUBULAR MEMBERS LINING AT LEAST A PORTION OF THE WALLS OF THE PASSAGEWAY AND FORMING PART OF SAID CIRCUIT DOWNSTREAM WITH RELATION TO FLOW THROUGH THE THROUGH-FLOW CIRCUIT OF SAID PARTITION WALL, AND ADDITIONAL TUBULAR MEMBERS LINING WALLS OF THE FURNACE AND ALSO FORMING PART OF THE CIRCUIT BUT DOWNSTREAM WITH RELATION TO FLOW THROUGH THE THROUGH-FLOW CIRCUIT OF THE PASSAGEWAY WALL TUBES, A CIRCULATING SYSTEM SUPERIMPOSED ON THE THROUGH-FLOW SYSTEM AND CONNECTED TO PROVIDE A SUPPLEMENTAL FLOW THROUGH SAID FURNACE WALL TUBULAR MEMBERS OVER AND ABOVE THE THROUGH-FLOW. 